1. Field of the Invention
The present invention relates to display supporting structures, and, more particularly, to a linkage supporting device used for supporting a display.
2. Description of Related Art
FIG. 1A is a schematic view of a conventional four-bar linkage structure. Referring to FIG. 1A, the four-bar linkage structure mainly has a first connecting frame 101, a second connecting frame 102, a mounting base 103, and a rotating shaft 104. The first connecting frame 101 and the second connecting frame 102 are pivotally connected between a rotating frame 105 and the mounting base 103. One ends of the first connecting frame 101 and the second connecting frame 102 are pivotally connected to the rotating frame 105 through the rotating shaft 104, and the other ends of the first connecting frame 101 and the second connecting frame 102 are pivotally connected to the mounting base 103 through another rotating shaft (not labeled). As such, the first connecting frame 101 and the second connecting frame 102 are arranged in parallel. In operation, a display disposed on the rotating frame 105 is moved to thus rotate the rotating frame 105 relative to the first connecting frame 101 and the second connecting frame 102 around the rotating shaft 104, thereby changing the angle of the display. Therefore, when the four-bar linkage structure is at a first limit position, a position limiting projection 1011 of the first connecting frame 101 abuts against a position limiting pin 1031 of the mounting base 103, and a position limiting notch 1021 abuts against a position limiting portion 1041 of the rotating shaft 104, thus limiting the display at a lowest position. FIG. 1B shows a second limit position of the four-bar linkage structure. Referring to FIG. 1B, a position limiting projection 1012 of the first connecting frame 101 abuts against the position limiting portion 1041 of the rotating shaft 104, and a position limiting notch 1021 of the second connecting frame 102 abuts against the position limiting pin 1031 of the mounting base 103, thus limiting the display at a highest position. Further, an extension spring (not labeled) is provided. The contraction force of the extension spring can be increased or decreased with different moving directions of the first connecting frame 101 and the second connecting frame 102 so as to offer enough supporting strength.
In the four-bar linkage structure, the first connecting frame 101 and the second connecting frame 102 are stacked so as to cooperatively operate to achieve position adjusting and limiting functions. However, such a four-bar linkage structure has a large size and cannot meet the demand for a shorter, thinner, lighter and smaller structure.
Therefore, there is a need to provide a linkage supporting device so as to overcome the above-described drawbacks.